Photograph of  improper condensate drain connected to plumbing vent line Air Conditioning condensate pumps, and their proper installation

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Air conditioner condensate pump guide:

This air conditioning repair article discusses the inspection of air conditioning condensate pumps & condensate pump control systems, including their proper installation.

This is part of our installation, inspection, & troubleshooting guide for condensate piping, traps, drains, condensate pumps, and the detection and hazards of air conditioning system condensate leaks in buildings.

We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.

CONDENSATE PUMPS - Air Conditioning Condensate Pump Installation & Repair

Photograph of an A/C condensate pumpAir conditioner condensate pumps are a convenient way to collect and dispose of the condensate produced by an air conditioning system when the air handler/cooling coil are located in a building location where the cooling condensate cannot be drained away by gravity.

The most common situation is the need to dispose of air conditioner condensate produced by an air handler which is installed in a building basement or crawl space.

[Click to enlarge any image]

Article Contents

How an Air Conditioner Condensate Pump Works

Air conditioner condensate is water removed from the building air as that warm, moisture-containing air moves across the cooling coil in the building's air conditioning system's air handler or blower unit. The photograph shown here is of a common air conditioner condensate disposal pump.

It's a little hard to see the pump's drain tube but it's that clear plastic tube in the upper left of this photo. If you are really alert you may have noticed those two capped-off copper tubes protruding from the concrete floor in the foreground of this photo.

This pair of tubes is a convincing indication that there was an oil tank, probably a buried oil tank, installed at this property - a topic that needs further investigation. See Oil Tanks - The Oil Storage Tank Information Website, for details on that topic. Don't let our focus on any individual building concern make us miss another, possibly important discovery.

The air conditioner condensate pump photo at the very top of this page shows an air conditioning condensate pump installed in an attic where it was used to move condensate across to a final condensate disposal point.

The white piping is a gravity drain that moves condensate from the attic air conditioner air handler down into the condensate pump reservoir.

We can't see much of the condensate reservoir because the installer placed this pump down into the attic floor (so that she could drain condensate into it by gravity).

The copper tube looping in the air is the drain line through which the condensate pump is moving condensate out of its reservoir to a disposal point. You can also see the black electrical wire bringing power to the condensate pump. The black round motor with a white label is the motor that powers the condensate pump.

The black rectangular device is a voltage transformer that converts the building's 120V to the voltage needed by the pump motor.

In the background of this interesting photograph we see a blue sump pump with a green garden hose connected to it. We surmise that the owner had previously tried to use this sump pump to remove condensate from the attic air handler. Stains suggest that the attic floor has previously been wet by air conditioner condensate spillage, perhaps leading to the more careful condensate pump installation shown here.

Sequence of Steps in the Operation of an Air Conditioner Condensate Pump

Proper and Improper Places to Route and Connect an Air Conditioner Condensate Pump Drain Line

Here is an excerpt from the Uniform Mechanical Code pertaining to the disposal of air conditioning condensate: "Section 310.0, 310.1 Condensate Disposal.

Condensate from air washers, air cooling coils, fuel-burning condensing appliances, the overflow from evaporative coolers and similar water supplied equipment or similar air conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area.

If discharged into the drainage system equipment shall drain by means of an indirect waste pipe.

The waste pipe shall have a slope of not less than 1/8 inch per foot (10.5 mm/m) or one percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size as required in either Section 310.3 or 310.4 below for air-cooling coils or condensing fuel-burning appliances, respectively.

Condensate or waste water shall not drain over a public way."

To clarify, an indirect waste pipe is something that is upstream of a trap. That means we cannot dump into anything downstream of a trap. That would include the main plumbing vent stack - a common error in disposing of air conditioner condensate in attic installations. -- [Thanks to Al Carson, Carson Dunlop Associates, Toronto]

Acceptable methods to dispose of air conditioning condensate from a condensate pump

Air conditioning condensate drain connections which are not recommended or are not best practice

Photograph of an ineffective condensate drain system - a bucket

Photograph of a float switchReader Question: Bad condensate sensor switch shuts down the air conditioner system

One of the condensate switch went bad, thereby shutting down the system.

I have to jumper ed the a/c line (yellow) to the hot(24 volts-red) on the ignition board to get the system to come back on while shopping for a new switch or pump.

I set the condensate pump to "continuous run" as a temporary measure to prevent flooding, but risk burning out the motor to the condensate pump.

- Yaga 8/13/11


Yaga additional risks from condensate leaks into a building when you bypass or "hot wire" the condensate overflow tray sensor switch are condensate leak overflow, building damage, and mold damage

Condensate Pump Operating Temperature Range

Question: maximum water temperature that can pass through the condensate pump

2016/07/20 Anonymous asked:
What is the maximum water temperature that can pass through the condensate pump. I have a Honeywell true steam humidifier that needs to be emptied and the maximum temperature gets to 140F.


Condensate pump temperature range

Anon: a typical HVAC condensate-handling pump can accept a maximum water temperature of 40oC / 104oF (Aspen pumps) or in some cases up to about 140F° (Diversitech pumps)

But there are other pumping systems designed for use with heating boilers or steam condensate that might suit for you.
For example an Aspen (brand) hot water / condensate pump can handle temperatures to 80oC / 176oF

Condensate Pump Sources

Here are some condensate pump sources that include higher-temperature handling pumps for hot condensate

What else goes wrong with air conditioning condensate pumps

Photograph of a damaged A/C condensate pump

In our experience these little devices are pretty reliable and useful. But a few things do go wrong, some more often than others.


Continue reading at CONDENSATE DRAINS, CODES or select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES below.

Or see CONDENSATE PUMP FAQs for questions & answers about condensate pump installation, inspection, troubleshooting, & repair and that were posted originally on this page.

Or see these

HVAC Condensate Articles

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